fuel vent line

[birddog486 21]

Anyone have pics of how there vent line is run? I have two wing tanks that I was thinking about teeing together with a valve on each and using the other header outlet for the vent but where does the vent line end so fuel doesnt siphon.

 

Travis

[EDMO 1078]

Travis,

According to Kitfox, the vent line is to be run between the right wing tank and the header tank, in theory, this connects both wing tanks and the header tank to prevent an airlock in the header.

EDMO

[kosseman 3]

my vent is hooked up from the header tank  to the top of the right wing tank

[birddog486 21]

Guys, this is on a c model avid and the wing tanks butt against the butt ribs. There are no connections to the top of the tank.

[EDMO 1078]

Travis,

I know little about the Avid tank/lines setups - but on a Kitfox without the extra hole near the top of the tank, the vent line can be run from the top of the header tank to a "T" fitting where the top of the sight gage connects to the wing tank.

EDMO

Edited 4 Sep 2013 by Ed In Missouri

[1avidflyer 1983]

Put a valve in the vent line.  after you vent the air out of the header, the vent is not needed.  I think most Avids had a tube sticking up through the butt rib on the right side.  (both my MK IVs did)  I had some problem with fuel siphoning out till I put a valve in the line.  Jim

[C5Engineer 1170]

I don't have a vent on mine. Both tanks are vented with the metal tubes inserted into the cap pointing into the slipstream. Both tanks have their own tube from the tank outlet to the header. I put a shutoff on the left wing tank right behind my head to prevent cross flow when it's parked. Both tanks burn fairly evenly and I've never had any issue with the header feeding before in 330 hrs.

[akflyer 1427]

I am with Joey. I had the recommended vent tube but it burped n leaked on my brand new lexan skylight the morning that my IA was coming over to do my condition inspection. I pulled the vent tube off and just have a shut off line on each wing tank. When you first fill up the plane open both tank valves and the header will vent to the empty tank. Once air is out of the header you can turn one tank or the other off. I have a poly header tank from KF and can see it inflight. I have never had it pull any air into the header in use. I normally only burn off one tank or the other after take off to keep the load balanced.

[wypaul 448]

I have the vent up through the right butt rib which is also my fuel gauge.  I tried several arrangements for the proper bend and direction of the tube to make this work.  The first was a "candy cane" shaped tube pointing to the wingtip which was fun to watch as it vented fuel as I flew along.    Next a ram tube to match the shape of the vent in the fuel tank lid, this worked but pushed the fuel down in the tube so that the gauge still would not function while in flight.  Finally I angled the vent at about 30 degrees off centerline and now I have a vent and a functional inflight fuel gauge.  The down side is that it only reads right at 5000 RPM (912) but by playing with the angle it can be set for any RPM.  I am still looking for a vent arrangement that will work for any RPM.

 

My vent is about 8" above the wing. 

 

If anyone has used this vent arrangement as a fuel gauge and found a tube arrangement that works throughout the RPM range I would like to hear what you have.

 

I will get some pictures when I get to the hanger if anyone is interested.

Edited 4 Sep 2013 by Paul S

[birddog486 21]

Thanks for the replys, I thought about going this route and I may also but, A couple of the forced landings I've read about over the last couple years were due to this arrangement.

 

What I took from those reports was: if there is a valve on both wing tanks and they are hooked to there own connection at the header without a specific vent line attached and one tank was allowed to introduce air into the line either from running to low on gas or maybe steep turns, the air trapped in the line wasnt able to force its way back up to the gas tank because of the ram air into that tank. If the other tank valve was opened it had the same result, the gas couldnt overcome the air bubble trying to escape and it stopped the flow. I'm not sure I believe all that but I guess its possible.

 

Ed, the Avids didnt have sight gauges either. These tanks have two outlets on the bottom only.

 

Travis

 

 

 

I don't have a vent on mine. Both tanks are vented with the metal tubes inserted into the cap pointing into the slipstream. Both tanks have their own tube from the tank outlet to the header. I put a shutoff on the left wing tank right behind my head to prevent cross flow when it's parked. Both tanks burn fairly evenly and I've never had any issue with the header feeding before in 330 hrs.

 

 

I am with Joey. I had the recommended vent tube but it burped n leaked on my brand new lexan skylight the morning that my IA was coming over to do my condition inspection. I pulled the vent tube off and just have a shut off line on each wing tank. When you first fill up the plane open both tank valves and the header will vent to the empty tank. Once air is out of the header you can turn one tank or the other off. I have a poly header tank from KF and can see it inflight. I have never had it pull any air into the header in use. I normally only burn off one tank or the other after take off to keep the load balanced.

[EDMO 1078]

Travis, This is very interesting - guessing that Dean didn't provide for a sight gage, and my Kitfox 1 did not have it either - just an unpainted "window" in the side of the tank to watch the gas slosh up and down. Denny must have started using the site gages - which are nothing new, being used on several planes in the past.

After listening to all of this - I believe that some have confused this header tank vent with the wingtank "vents", which not only relieve pressure on the tanks, but provide a positive pressure for better fuel flow. This vent prevents airlocks.

I am of the opinion that your idea of running a line between each of the wingtanks and putting in a "T" with a line going to the header tanks MIGHT - underscore MIGHT - be the answer to your problem, because fuel pressure and fuel weight from either tank should over-ride the air from the other tank.

But, asking this - this line would not be your fill lines from each tank? It would be T'd from the fill lines, and then T'd to the header vent line? That might be more foolproof, than just a T off of your main fill lines to the header tank?

But, what might be much simpler, is just to build a boss near the top of your tank, and run the header vent line to that - It would only take a small hole in your tank - You could make a sight gage this way too.

BTW: The Kitfox site gages have a homemade restrictor in the bottom fitting with only a very small hole in it to keep the level in the gage more constant.

There might be a chance, that if you ran one tank dry, and air got into the "T"d line to the header, and then you shut off the valve to the empty tank, before fuel from the full tank filled the line, that you might have an airlock - but think this is minimal chance, since you are going to flow from both tanks 99% of the time.

I am having a hard time visualizing a gage that is open to the airflow outside of the plane - just don't make much sense to me. I would be tempted to cut a hole in the side of the tank and put in one of the gages that use a float action, or build up some bosses with epoxy or 9460 and drill and tap them to make my own sight gage like Kitfox and Piper use.

Photos are always interesting - They help us visualize what we are supposeded to talk about. I write while searching for ideas and solutions - just trying to help - if you don't want to do what Jim and Leni have suggested.

EDMO

Added thought: I would NEVER, EVER, put an electric gauge in my fuel tanks - Just too much risk involved in combining electricity and gasoline, IMO.

Edited 5 Sep 2013 by Ed In Missouri

[wypaul 448]

I made it out to the hanger and took a couple of pictures of the Vent/Gauge setup that I am using.  This is plumbed to the top of the header.

 

[EDMO 1078]

I made it out to the hanger and took a couple of pictures of the Vent/Gauge setup that I am using.  This is plumbed to the top of the header.

Paul, I see a chart there - does this vent line accurately show the amount of gas in your tank too? On the ground, or in flight too?

EDMO

Edited 5 Sep 2013 by Ed In Missouri

[EDMO 1078]

Afterthought to my ramblings above - You could use epoxy or 9460 to bond aluminum female fittings to the side of the tank and not worry about having to drill and tap the holes - a very small hole behind the fitting into the tank would be enough for a vent or sight gage.

EDMO

[wypaul 448]

Paul, I see a chart there - does this vent line accurately show the amount of gas in your tank too? On the ground, or in flight too?

EDMO

On the tailwheel it shows about four gallons of fuel less than what is contained in both tanks.  As I mentioned in the earlier post it now reads what is in the tanks at 5000 RPM while in flight.

 

 

Afterthought to my ramblings above - You could use epoxy or 9460 to bond aluminum female fittings to the side of the tank and not worry about having to drill and tap the holes - a very small hole behind the fitting into the tank would be enough for a vent or sight gage.

EDMO

 

If I had it to do over I would probably go that route Ed and may sometime in the future but at the moment I am not in any hurry to contaminate the tank by drilling into it.  Maybe this winter I will build an air powered vacuum and tackle that project.

[C5Engineer 1170]

I have 1" wide unpainted or covered strips of the ends of my tanks exposed that you can see through the wood rib. I leveled the plane and added fuel 1 gallon at a time marking them starting with 2-12 gallons. The last two gallons are above the exposed tank area I can see. In level flight a small rock of the wings shows you the level plus or minus a gallon due to sloshing of what's in there. I also marked 5 and 10 gallon marks with it sitting on the tailwheel on the other side of the strip for when I'm getting ready to go and fly I can just give the plane a shake and get a good wag of how much fuel I have. Sometimes it's hard to see if the sun is just right but between the hobbs, my fuel flow computer, and visually confirming what is in the tank I feel much more comfortable with my duration left than I ever did in a Cessna. I plan for 5 gph when I'm going X-country. With 4 hours + duration it's never been much of an issue going X-country. It's the days when were out playing hopping from strip to strip that you have to pay attention to it.

[EDMO 1078]

On the tailwheel it shows about four gallons of fuel less than what is contained in both tanks.  As I mentioned in the earlier post it now reads what is in the tanks at 5000 RPM while in flight.

 

 

 

If I had it to do over I would probably go that route Ed and may sometime in the future but at the moment I am not in any hurry to contaminate the tank by drilling into it.  Maybe this winter I will build an air powered vacuum and tackle that project.

Paul,

I don't think a small drill would contaminate your tank - I'm talking about a hole as small as 1/32 and not larger than 1/16 inch. By bonding a female fitting, or two, to the side of the tank, you eliminate the larger hole and threading. Just an idea that came to me while writing last night.

EDMO

[wypaul 448]

Good point ED, thanks.

[wypaul 448]

I did clean off a section on the end of the left wing last time I had them off but did not remove the fabric from the butt rib so it was visible.  Need to get around to completing that.  Maybe manana.  Thanks for the reminder.  Oh, I did buy the rudder pedals from Michael but haven't installed them yet.  Very nicely built. 

[avidchh 3]

These Rochester fuel gauges work great and aren't too costly.

[EDMO 1078]

These Rochester fuel gauges work great and aren't too costly.

Do you have a part number and a price for the gauges?

Was there any problem calibrating them for the tanks?

This solves the missing gage problem, but does not solve the header tank vent problem.

Thanks,

EDMO

Edited 6 Sep 2013 by Ed In Missouri

[dholly 718]

I had one of those dial gauges in my KF3 wing tank. Never leaked. Easy to see fuel level with a very quick glance. Wish I had them in my KF4 tanks, much harder to see fuel level with sight gauge IMHO. Thinking of installing the Belite LED gauge this winter, saw them at OSH and Kitplane Mag just did a little write up.

[wypaul 448]

These Rochester fuel gauges work great and aren't too costly.

Can you tell us a little about how they are installed.  Were nutplates installed to screw the gauge into?

[wypaul 448]

I had one of those dial gauges in my KF3 wing tank. Never leaked. Easy to see fuel level with a very quick glance. Wish I had them in my KF4 tanks, much harder to see fuel level with sight gauge IMHO. Thinking of installing the Belite LED gauge this winter, saw them at OSH and Kitplane Mag just did a little write up.

The Belite gauge looks good.  What sort of sender are you thinking about and I assume that it would be in the end of the wing and tank.

[avidchh 3]

Do you have a part number and a price for the gauges?

Was there any problem calibrating them for the tanks?

This solves the missing gage problem, but does not solve the header tank vent problem.

Thanks,

EDMO

 

http://www.aircraftspruce.com/catalog/inpages/mech_fuel_gauge.php?clickkey=39672

http://www.aircraftspruce.com/catalog/pdf/05-16700.pdf

 

Easy to install and calibrate. I have the std header vent you can see part of in the pic. Bend faces aft. No issues. I did install a low fuel sensor in the header tank when I rebuilt following my fuel line clog accident. Gives me 2 full gals reserve at the sensor.

Edited 6 Sep 2013 by Stephen N613HH